Toner feed



R R. ULARY March 29, 1966 TONER FEED Filed Feb.

INVENTOR. 2055511 2 I/AA'AY AM'EA/T United States Patent 3,242,902 TONER FEED Russell R. Ulary, Levittown, N.J., assignor to Radio Corporation of America, a corporation of Delaware Filed Feb. 20, 1963, Ser. No. 259,930 3 Ciaims. (Cl. 118-637) This invention relates to the development of electrostatic images and more specifically to improved means for controlling dispersion of toner material in a liquid developer composition.

In the art of electrostatic printing various methods are employed to develop electrostatic images. One such method is known as liquid development. In this method, electrostatic images residing on a surface are developed by applying to the surface a dispersion of finely-divided toner in an insulating carrier liquid. During development, the toner is electrostatically extracted from the carrier liquid and held on the surface in an image pattern. Liquid development of electrostatic images is described in many publications and patents, one of these being US. Patent 3,053,688 issued September 11, 1962, to Harold G. Greig.

Liquid development of electrostatic images provides many advantages over other developing methods. However, it has been found that, during development of one electrostatic image after another as occurs in equipment such as automatic oflice copiers, the toner component of the liquid developer rapidly becomes depleted resulting in progressively poorer print quality, Should one attempt to overcome this difficulty by initially including excess toner in the liquid developer, the resulting prints will have an unacceptable amount of toner adhering in nonirnage or background areas until enough prints have been made so that the excess toner has been extracted from the liquid developer.

Accordingly, it is a general object of this invention to provide improved means for maintaining an appropriate quantity of toner in a continuously used liquid developer.

It is another object of this invention to provide improved means for adding controlled amounts of toner to a liquid developer.

It is a further object of this invention to provide improved liquid developing apparatus including means for adding controlled amounts of toner to the liquid developer employed therein.

These and other objects and advantages are achieved in accordance with this invention by providing a container at least partially filled with toner and so constructed that toner can be caused to bleed from the container at a controlled rate. In a specific apparatus embodying the invention, a container, such as a cylinder of metal or plastic, is filled with a mass made up of toner particles dispersed in a soluble host material such as, for example, silicone grease. At least one aperture communicates with the interior of the container so that the liquid component of a developer composition can come in contact with the grease in the container. The liquid gradually dissolves the grease and causes toner to bleed from the container thus adding toner to the developer composition at a controlled rate.

The apparatus includes a reservoir designed to contain liquid developer, an applicator head of known design for applying the liquid developer to an electrostatic image, and conduit means for supplying liquid developer to the applicator head as well as for returning liquid developer to the reservoir from the applicator head. In the flow path of the liquid developer a receptacle is provided for the grease-filled container, in the grease of which the toner particles are dispersed. This receptacle is designed to hold the container in position with its aperture or aper- 3,242,902 Patented Mar. 29, 1966 ice tures in the flow path of the liquid developer. Each time a metered amount of liquid developer flows from the reservoir to the applicator head and back to the reservoir, a metered amount of toner bleeds from the container into the developer liquid.

Additional objects and advantages are included in the following detailed description which refers to the accompanying drawings wherein:

FIGURE 1 is a plan view partially in section of a developer cartridge in accordance with this invention.

FIGURE 2 is a plan view of an alternative embodiment of the developer cartridge of FIGURE 1.

FIGURE 3 is a side elevational view, partially in section, of improved developer apparatus in accordance with this invention.

FIGURES 3A and 3B are fragmentary views, partially in section, of modifications of the apparatus of FIG- URE 3.

Similar reference characters are applied to similar elements throughout the drawings.

DEVELOPER CARTRIDGE The container in the form of a developer cartridge 11, as depicted in FIGURE 1, comprises a hollow cylinder at least partially filled with a grease 13 consisting of electrcscopic toner particles dispersed in a soluble host material. Suitable materials will be described in more detail hereinafter. The cartridge 11 is closed at one end 15 and open at the other end 17. Slots 19 are cut through the wall of the cartridge near its open end 17. For convenience in handling, a cap 21 is provided which fits over the open end 17 and covers the slots 19 in the cartridge wall. The cap 21 is removed when the cartridge 11 is to be used. The cartridge 11', depicted in FIGURE 2, is similar to the one shown in FIGURE 1 except that both ends are closed and a plurality of holes 23 are cut through the cartridge wall. 1

DEVELOPER PASTE In making up the grease or paste 13, contained in the cartridges 11 and 11 of FIGURES l and 2, the components thereof can be selected from many materials. The toner particles in the mass may be any of those commonly used in the art of electrostatic printing. The soluble host material also may be selected from a wide variety of materials but, preferably, is selected to have insulating properties. While the host material may comprise a solid, such as a wax, it is preferred that it have the consistency of a grease or a petroleum jelly when mixed with the toner. The host material should be soluble in the carrier liquid and should also be chemically inert with respect to the carrier liquid. The host materials in the following examples are readily soluble in the carrier liquids most commonly used in electrostatic printing. Such carrier liquids include low viscosity silicone oils, trichlorotrifiuorethane, and many hydrocarbon solvents. At the same time, the toner particles should be substantially insoluble in the carrier liquid.

Example 1 A black toner is prepared by making two solutions:

Solution one comprises:

6 grams Iosol Black (Cl. Solvent Black 13) 400 grams methanol Solution two comprises: 9 grams Spirit Nigrosine (CI. 50415 400 to 600 grams methanol the mixture is filtered and the filter cake allowed to dry. The dried filter cake is broken up and ball milled. After ball milling the black pigment is classified as to particle size. Particles having a diameter of 74 microns or less are preferred.

A developer paste is prepared by thoroughly dispersing 60 grams of the above toner in 160 grams of a silicone oil such as Silicone DC 200 marketed by the General Electric Company. The toner and oil mixture is ball milled for about four hours and filtered to remove silicone oil. 40 grams of the resulting paste are then mechanically mixed with 20 grams of a silicone grease, such as Dow Corning High Vacuum Grease, and the cartridge 11 or the cartridge 11' filled therewith.

Example 2 An alternative developer paste can be prepared with:

60 grams toner 160 grams silicone oil, viscosity about 2 centistokes 5 grams silica aerogel such as CAB-OSIL marketed by Godfrey L. Cabot Industries.

2.4 grams powdered iron The above ingredients are ball milled for about four hours and then filtered. Filtering removes excess silicone oil and provides a developer paste to be inserted in a cartridge.

Example 3 A petroleum jelly (Vaseline) is substituted for the silicon grease in Example 1.

Other suitable developer pastes are described in US. Patent 3,038,799 issued June 12, 1962, to K. A. Metcalfe et al.

It is well known that an electrostatic image on an insulating layer can be developed by immersing the layer in a tray containing a liquid developer composition of toner particles dispersed in an insulating liquid. When developing many prints in this manner, the developer composition is rapidly depleted of toner particles so that, after a time, development becomes entirely inadequate.

A continuous supply of toner can be added to a developer composition at a controlled rate with a developer cartridge filled with a paste or grease prepared in accordance with the above examples. The cartridge may be like one of those illustrated in FIGURE 1 or 2, and immersed in a tray of insulating carrier liquid. During the process of making one print after another, the insulating carrier liquid in the tray penetrates the slots 19 and the open end 17 of the cartridge 11 (FIGURE 1) or the holes 23 of the cartridge 11' (FIGURE 2). The insulating liquid penetrating the cartridge dissolves the host material contained therein and causes toner particles to bleed out of the cartridge and replenish the toner supply in the developer composition.

The improved developer apparatus shown in FIGURE 3 is particularly adapted for developing electrostatic images on an insulating surface of a flexible web 31. Such a web may be a web of electrophotographic paper as described in US. Patent 3,052,540 issued September 4, 1962, to Harold G. Greig. The apparatus includes two pressure rollers 35 and 38 which engage the paper 31 and which are driven to transport the paper through a portion of the developer apparatus. Liquid developer composition is applied to the upper pressure roller 35 by means of an applicator 37. The developer composition is supplied to the applicator 37 through a pipe 39 connected to a centrifugal pump 41. As liquid developer composition is carried by the upper pressure roller 35 into contact with the paper a turbulent nip 43 of the developer composition is formed where the roller 35 contacts the paper. This turbulent nip 43 substantially enhances development of electrostatic images on the paper and also enhances clean up of developer material which may adhere in areas on the paper 31 where devleoper is unwanted. The developer composition not only forms the nip 43 but also flows down the face of the paper 31 as it is carried over the pressure roller 38. The developer composition is thereby caused to be in contact with a substantial portion of the paper 31 during development.

Developer composition, in excess of that used to develop an image on the paper, drops therefrom into a tray or sump 45 positioned below the two pressure rollers 35 and 38. The collected developer composition 47 is returned through pipes 49 to a reservoir 51 which also contains the centrifugal pump 41.

In a preferred embodiment, means are provided for inserting the developer cartridge 11 of FIGURE 1 in the path of flow of the developer composition through the return pipes 49. A receptacle 53 for the cartridge 11 is provided. The cartridge 11 is inserted through a sleeve 55 on the receptacle 53 and into a hole or well 57 drilled in the receptacle 57. The well 57 has a suflicient diameter to provide ample clearance for liquid to flow around the outside of the cartridge. Two holes 59 and 61 communicate with the well 57 in which the cartridge sits and provide means for developer composition to contact the cartridge 11 when flowing back to the reservoir 51 through the pipes 49.

Alternative arrangements for using the developer cartridge to replenish toner in the apparatus of FIGURE 3 are also contemplated as shown in FIGURES 3A and 3B. For example, toner cartridge 11 (FIGURE 2) may be positioned, as shown in FIGURE 3A, in the sump 45 and held therein by a spring clip 69. As a second alternative, the toner cartridge 11 can be mounted in the reservoir 51. Such mounting is shown in FIGURE 33, by way of example, with the cartridge 11' positioned on the pump 41 and held thereon by a spring retainer 71.

By inserting the developer cartridge 11 in the sump 45 (FIGURE 3A) or the cartridge 11 in the receptacle 53 (FIGURE 3) advantages are realized which cannot be readily attained when the cartridge 11' is mounted in the reservoir 51 (FIGURE 33). Such advantages become apparent when the paper is moved one frame at a time by intermittently driving the rollers 35 and 38. In such a case, it is desirable that the pump 41 also operate intermittently so that developer composition is applied to the paper 31 only while it is being advanced by the pressure rollers 35 and 38. During such operation, developer composition collected by the sump 45 and flowing back to the reservoir 51 causes toner to bleed from the developer cartridge 11 in the sump 45 (FIGURE 3A) or the developer cartridge 11 in the receptacle 53 (FIGURE 3) only once during each cycle of operation. It has been found that, with a toner cartridge 11 (FIGURE 1) having a diameter of about inch, a length of about 2 /8 inches and filled with about 11 grams of developer paste, developer apparatus can operate as described to produce at least 200 8 /2" x 11" prints.

Mounting of the developer cartridge 11 in the reservoir 51 (FIGURE 3B) may result in a continuous bleeding of toner from the cartridge 11'. Hence, it is desirable that the developer apparatus of FIGURE 33 be employed in a substantially continuous printing operation rather than an intermittent operation.

Since the liquid component of the developer composition in the reservoir 51 may also become depleted as by being carried off on the paper 31, means are provided for added increments of insulating carrier liquid from time to time as shown in FIGURE 3. Such means may comprise a container 63, a solenoid pump 65 and a conduit connecting the pump 65 with the reservoir 51.

What is claimed is:

1. Liquid developing apparatus comprising:

a reservoir for containing a liquid developer composition;

applicator means for applying said composition to a surface bearing an electrostatic image;

conduit means defining a flow path for said composition from said reservoir to said applicator means and back to said reservoir;

means including a mass of toner particles dispersed in a soluble host material in said flow path to cause toner particles to bleed into said composition when it flows through said path.

2. A liquid developer apparatus comprising:

a reservoir for containing a liquid developer composition;

applicator means for applying said composition to a surface bearing an electrostatic image;

conduit means for supplying said composition to said applicator means from said reservoir;

sump means for collecting developer composition draining from said surt'ace;

conduit means for returning said composition to said reservoir from said sump means;

said sump means and both said conduit means defining a flow path for said composition from said reservoir to said applicator means and back to said reservoir;

means including a mass of toner particles dispersed in a soluble host material in said flow path to cause toner particles to bleed into said composition when it flows through said path.

3. A liquid developer apparatus comprising:

a reservoir for containing a liquid developer composition;

applicator means for applying said composition to a surface bearing an electrostatic image;

conduit means for supplying said composition to said applicator means from said reservoir;

sump means for collecting developer composition draining from said surface;

conduit means for returning said composition to said reservoir from said sump means;

said sump means and both said conduit means defining a flow path for said composition from said reservoir to said applicator means and back to said reservoir;

a toner feed cartridge comprising an apertured container at least partly filled with a developer paste of toner particles dispersed in a host material soluble in said host material;

means for positioning said cartridge with its apertures in said flow path to cause toner particles to bleed from said cartridge when said composition flows through said path.

References Cited by the Examiner CHARLES A. WILLMUTH, Primary Examiner.

WILLIAM D. MARTIN, Examiner. 

1. LIQUID DEVELOPING APPARATUS COMPRISING: A RESERVOIR FOR CONTAINING A LIQUID DEVELOPER COMPOSITION; APPLICATOR MEANSA FOR APPLYING SAID COMPOSITION TO A SURFACE BEARING AN ELECTROSTATIC IMAGE; CONDUIT MEANS DEFINING A FLOW PATH FOR SAID COMPOSITION FROM SAID RESERVOIR TO SAID APPLICATOR MEANS AND BACK TO SAID RESEVOIR; MEANS INCLUDING A MASS OF TONER PARTICLES DISPERSED IN A SOLUBLE HOST MATERIAL IN SAID FLOW PATH TO CAUSE TONER PARTICLES TO BLEED INTO SAID COMPOSITION WHEN IT FLOWS THROUGH SAID PATH. 